a6retrofit

23.6.2009 (updated 17.1.2010) - LoCal sent the following contribution about tyre and vibration issues reported in Audi forums and related solutions.
Based on frequent topics and questions on Audi forums, I decided to gather up some often repeated worries, solutions and information regarding various kinds of chassis or steering vibration issues in Audi B8 platform cars, the new Audi A4 and Audi A5 (and their S variants). Much of the solutions linked here point to universal tyre/wheel related websites and articles (that are relevant with any car), but I am looking at things from an Audi B8 perspective here in my own article.

Audi changed a lot of things in the underpinnings of the car when they designed the B8 platform. The car is now less front-heavy than Audis of the past, but it also seems to be sportier and more vulnerable to tyre/wheel imbalance and imperfections. These issues are not uncommon in sport cars, the farther (read: bigger) you go in wheel size and sportier drive (read: harder, more direct), the more important it is to have your wheels and tyres in check - and, conversely, the harder it is to keep them that way.

Arguably, the A4 and A5 are not sport cars, so some of the issues people have been having are grounds for warranty repairs and future improvements by Audi. Other issues are likely reasonably solved with some knowledgeable help in choosing and balancing your tyres and wheels. I'll try to cover some of this ground in this article and point to links and techniques you might want to research further.

The most common vibration issue, judging from forum postins, with A4/A5 are vibrations in steering wheel at highway speeds. A long-running thread at A5OC.com is a good place to read about it:

To cut a long story short, a lot of people are experiencing steering wheel shimmy or vibrations or shaking at highway speeds, around 100 km/h (or arond 60 mph). Lower the speed significantly, it goes away - higher the speed significantly, it also goes way. The shimmy also seems to come and go. It may develop over time, manifest itself mostly only with cold wheels, but it may also come and go - yesterday it was there, today it isn't and so on.

Again, steering wheel vibrations are not uncommon in cars, usually they are related to wheels not being in balance, but this seems to manifest itself rather often in A4/A5. This issue seemed to be enough of a "feature", that Audi of America released a Technical Service Bulletin or TSB (44-08-04) about how to fix it. This service bulletin exemplifies some of the notable techniques I wanted to point out in this article and that you should consider if you have issues:

Technical Service Bulletins for A5/S5
http://www.a5oc.com/forums/showthread.php/technical-service-bulletins-6324/index.html

What the technical service bulletin suggests, is that the problem is caused by imbalanced wheel/tyre assembly and/or too high road force values in some of the wheels or damaged wheels/tyres. It suggests balancing the tyres, measuring their road force values and placing the lowest road force value wheel to left front, second lowest to right front, third to left rear and last to right rear. If it is not possible to reduce the road force value below 27 lbs, the bulletin suggests replacing the particular tyre.

Audi of America did this under warranty (experiences in other countries differ, much of the time maintenance shops find nothing wrong with the car or no remedies available), but results were mixed. It might help for a while, but as the tyre wears out, imperfections start to creep in and the problem again starts coming and going. Some have certainly gotten used to it as a feature of the car, but others have been pressing Audi for more of a solution. While waiting for a solution, various fixes were tried, some more successfully than others. One poster in the thread above listed the following suggestions that had helped him (I added a few bulletpoints as well as some comments to the list):

- Make sure your wheels are aligned properly (this should also help with any directional instability).
- Make sure your wheels are centered and tightened properly (so that they are not rolling off center).
- Make sure your wheels are balanced (don't assume your balancing shop did a perfect job either, try another shop). Also make sure no balancing weights have fallen off.
- Check tyre pressures so that they are manufacturer recommended (recommended tyre pressures are listed in a sticker in the inner edge of the drivers door).
- Check if the problem occurs only with cold tyres (problem might point to flat spotting, see below, or just your wheel type just taking their time to start working).
- Move front wheels to back or the ones with lower road force to front (and to see if the problem goes away or moves to back which might point out a problem tyre or wheel).
- Make sure your wheels (especially front wheels) have worn out equally, if you have to replace one wheel, remember to replace both at the same time.
- Some also have tried with varying success to change tyre pressures to other than manufacturer recommended, like increasing tyre pressure.
- Make sure there is no wheel (bent wheels? did you hit a curb?) or tyre damage.
- Research your tyres and wheels before purchase to get experiences on how they behave on picky cars such as the A4/A5.

Remeber to measure tyre pressure always when the tyre is cold. Warmer tyre will report a higher pressure. However, you should note that changing tyre pressures to other than manufacture recommendations can have a detrimental effect in other ways - read more:

Now, one other potential issue mentioned above concerns cold tyres and, like many wheel issues, is worse with larger wheels (where there is less air and rubber between the wheel and the road). This phenomenon is called flat spotting and usually happens when the car is parked for a while. The area of the tyre the car is sitting on gets flattened, usually temporarily but sometimes permanently, thus creating an imprefection in the roll of the tyre/wheel - and creating vibrations and, maybe, initially even a bit of bumpy ride until the wheel warms up.

To avoid flat spotting, some suggest storing cars for a longer period (like winter storage) lifted up, instead of standing normally on their tyres.

Starting from around November 2008, information about new camber settings and control arms / bushings or wheel bearing housings from Audi started circulating forums. Apparently Audi was incorporating these changes to at least the Audi A5 lineup from November 2008 (from VIN 28001 m.y. 2009?) and was also offering the retrofit as a warranty repair in some markets for those with vibration issues. Apparently the new parts should be less picky (Audi TSB number 2017475?). Notes and part numbers:

Reports on the success of the changes are far and few between, and seem inconclusive - as do the reports on vibrations in general. Problems with wheels, tyres and related vibrations seem quite individual in nature and so do any solutions apparently.

Some of what is covered above has also been reported for Audi A4 B8 in forums, so it does seem like a feature of the B8 platform, not just of Audi A5.

If you are experiencing some other kinds of vibrations, such as chassis vibrations, it is quite possible they are related to wheels. Check the above check-list and the links (or Google these concepts to learn more - above links are just examples, I'm sure there is a lot more good links out there) on tyre/wheel alignment and balancing, road force values, tyre pressures and flat spotting of tyres. Of course it could be an issue in the cars axles or something more sinister, but tyres and wheels are a good place to start the hunt.

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UPDATE 15.10.2009:

The vibration continues to be a hot topic in many Audi B8 platform forums, ranging from A4 B8 to the S5. Here is another example:

The current concensus seems to be that the B8 platform is excessively picky about wheel etc. imperfections, that can easily lead to vibrations. Sometimes replacing wheels, road force balancing them or a multitude of above-mentioned tricks help. Replacing control arms with new ones (that supposedly roll of the factory from now on in new cars) seems to help in many cases where other tricks didn't help - but not necessarily always. Even with the new control arms, the car may remain pickier than usual about wheels, spacers, whatnot.

Audi seems to acknowledge the problem differently in different markets, ranging from complete denial to seemingly the most progressive and customer-oriented Audi of America, which has issued several technical service bulletins (TSBs) on this as noted earlier in this article: first the road force balancing solution, then a bulletin replacing control arms with new ones (apparently with different bushings) if road force balancing/replacing wheels does not help and thirdly a bulletin on what kind of special tools to use on the B8 platform for accurate road force balancing. In some markets the response has been "affects U.S. cars only", when the online reality suggests this affects many B8 cars in most all markets.

Joining the pickiness-related vibrations (that may occur in motorway speeds or when braking), seems to be a new vibration issue, reportedly acknowledged by Audi of America (http://forums.audiworld.com/showthread.php?t=2761846). A low speed shuddering has been reported to happen at very low speeds. This may be related to the steering system hose, with a fix from Audi forthcoming perhaps in the months to come. The Saga continues!

In this article replacing/road-force balancing front wheels wasn't enough, but replacing four lower-front control arms in A4 and S5 solved the problem. According to the article the replacement arms are the same size as the old ones, but their bushing stiffness is different.

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UPDATE 7.8.2009 / 25.9.2009:

This news of Audi of America endorsing Haweka wheel balancer tooling especially with regards to A4, A5 and S5 (only these models are mentioned in the press release by the tool-supplier) to provide "more accurate road force balancing results", adds to the evidence that the B8 platform is really picky about its wheels:

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